<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  <script>
  var message = "Hello World"
  //获取自字符串
  console.log(message.slice(3,7))
  console.log(message.slice(3,-1))
  console.log(message.slice(3))

  //substr
  console.log(message.substr(3,7))
  
  
  </script>
</body>
</html>